A conventional electron column is generally operated in such a way that an electron emitter emits electrons, a source lens forms the electrons as electron beams, a deflector deflects the electron beams, and a focusing lens focuses the deflected electron beams onto a sample.
There is an example in which a magnetic deflector is used in an electron column, but such a magnetic deflector is used in a large-sized electron column and is merely a typical magnetic deflector that is very large.
Therefore, in a conventional microcolumn, such a deflector mainly deflects electron beams using an electric field.
FIG. 1 is a sectional view conceptually showing a 1 KV microcolumn based on the concept of a well-known Scanning Tunneling Microscope (STM) alignment field method as a representative microcolumn. In FIG. 1, a source lens 1, a deflector 2 and an Einzel lens 3 are shown. An electron emitter 5 attached to an STM-type positioner emits an electron beam 6 onto a sample surface 9. Such a beam 6 passes through the source lens 1, composed of silicon microlenses, for example, an extractor having a diameter of 5 μm on the central axis thereof an acceleration electrode having a diameter of 100 μm, and a limiting aperture having a diameter of 2.5 μm. The deflector 2 is placed below the source lens 1. The deflector is composed of eight electrodes, as shown in the plan view A on the right side of FIG. 1, and scans the electron beam emitted from the source lens 1. Thereafter, the electron beam 6 passes through the Einzel lens 3. Such an Einzel lens is composed of silicon microlenses having a diameter of 100 to 200 μm, and silicon holes having a thickness of 1 to 2 μm and a size of 1×1 mm are formed in the center of the microlenses. Respective silicon layers are separated and spaced apart from each other by a predetermined interval using an insulating spacer. Thereafter, the electron beam 6 is incident on the sample surface 9, so that secondary electrons are emitted and are detected using a Channeltron detector or the like.
Generally, the above lenses and detector are manufactured as electron lenses through a Micro-electro-mechanical systems (MEMS) process and are used. Of course, a deflector can be used through the use of a conductor wire, but is also manufactured through an MEMS process to realize precision as well as the convenience of manufacture of an electron column. However, electron lenses generally function as optical lenses using an electric field or a magnetic field, and a deflector also generally performs deflection using an electric field. However, in the case of an electric field, a spherical aberration or a color aberration is poor, or a high voltage of about 100V must be applied, in the case of the lenses. Therefore, it is difficult to use a typical magnetic deflector due to the size of a microcolumn in a current situation, and thus the development of a magnetic deflector usable for a microcolumn is required.